<?php
// 箭头函数
$y = 1;
$fn1 = fn($x) => $x + $y;
// 相当于
$fn2 = function ($x) use ($y) {
    return $x + $y;
};
var_export($fn1(10));
var_export($fn2(20));
$z = 1;
$fn3 = fn($x) => fn($y) => $x + $y + $z;
var_export($fn3(1)(20)); // 22
$aaa = '小明';
$bbb = '小李';
var_dump(compact('aaa', 'bbb'));
